The study is designed to correlate host defense mechanisms with the development of nosocomial infection. Four groups of patients are being studied prospectively: aged, diabetic, renal graft recipients, and patients with solid tumors. To date the most complete results are in the aged. Alterations in Ig levels and lyphocyte function with increasing age have been documented in individuals free of disease and receiving no medication known to alter the immune or inflammatory response. Pharyngeal colonization with gram negative bacilli or S. aureus occurred with increasing frequency with increasing age. Nosocomial pneumonia was not noted in the under 45 years of age hospitalized control group, however, three cases were diagnosed in the group over 60. This rate of attack was four times that reported for general hospital populations in a national survey. Information derived from the other three study groups is too preliminary to report. BIBLIOGRAPHIC REFERENCE: Baird, I.M., Slepak, J.M., Kauffman, C.A. and Phair, J.P. Nosocomial infection with Gentamicin-Carbenicillin resistant Pseudmonas aeruginosa. Anti. Ag. Chemo. 10: 626, 1976.